Experiment 10-1 - Lab Reort PDF

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EXPERIMENT 10 GENERAL CHEMISTRY 1 SCC 2

TITLE OF EXPERIMENT

DETERMINATION OF THE GAS LAW CONSTANT

INTRODUCTION The purpose of this laboratory experiment is to determine the value of Gas Constant R and used the Gas Law to solved problems. This goal was accomplished by measuring the sample of magnesium to react with hydrochloric acid at certain temperature and pressure so that the precise volume of the hydrogen gas could be determined and the value of R could be calculated using the gas equation PV= nRT P ⎯ pressure, V ⎯ volume, n number of moles, T⎯ temperature MATERIALS _ - Ring stand - Test tube

- Clamp - Glass syringe - Beaker - Tweezer - Measuring pipet - Measuring balance COMPOUND OR CHEMICAL - Magnesium metal (Mg) - 0.5M Hydrochloric acid (HCl) - 1.0M Hydrochloric acid (HCl) METHODS - Glass syringe and tube were clamp to ring stands separately. - Magnesium metal with oxide was cleaned with 0.1M hydrochloric acid (HCl). - The clean magnesium metal was weigh between 0.013 ⎯ 0.018 grams on the balance. - A clean tube was filled with 4mL of 1M HCl and the magnesium metal was placed in and waited for 3 ⎯ 5 minutes for the metal to melt. - The final volume of the gas on the syringe was recorded on the data sheet.

DATA DETERMINATION 1 0.0133

2 0.0162

3 0.0167

Moles of Mg

5.472∗10−4

6.665∗10−4

6.871∗10−4

Moles of H2

5.472∗10−4

6.665∗10−4

6.871∗10−4

0

0

0

Mass of Mg (grams)

Initial syringe reading (mL)

Final syringe reading (mL)

12

15.5

16.0

Volume H2 collected (mL)

12

15.5

16.0

0.012

0.0155

0.016

Temperature (ο C)

20

20

20

Temperature (K)

293

293

293

Barometic pressure (mmHg)

751

751

751

Vapor pressure of H2O (mmHg)

17.5

17.5

17.5

Correct pressure (mmHg)

733.5

733.5

733.5

Correct pressure (atm)

0.965

0.965

0.965

Calculated R value (Latm/mol-K) Average R value (L-atm/molK) True R value (L-atm/mol-K)

0.072

0.077

0.077

Volume H2 collected (L)

0.075 0.082

% error of average R

8.537%

CALCULATION 1.Balance equation for the reaction of the magnesium metal and hydrochloric acid.

2.Mole of Mg

Mg + HCl → MgCl + H2 Mass of Mg / Molar Mass of Mg 0.0133 / 24.305 = 5.472 ∗ 10−4

3.Volume of H2 in liters

12mL ∗ 1 L / 1000mL =0.012L

4. Temperature converted Kelvin 20οC + 273 =293 K

5. Corrected pressure in mmHg: Barometic pressure − Vapor pressure of H2O 751 − 17.5 = 733.5 6.Correct pressure in atm:

733.5mmHg ∗ 1atm / 760mmHg = 0.965

7. The R value, L-atm / mol-K

R= PV / NT 0.072 = 0.965 ∗ 0.012 / 5.472∗10-4 ∗ 293

8. Average R value

0.072 + 0.077 + 0.077 = 0.226 / 3 = 0.075

9. Percentage error of average R: true value of R − average value of R 0.082 − 0.075 = 7∗10-3 -3 7∗10 = 0.007 0.007 / 0.82 ∗ 100% = 8.537% DISCUSSION In the experiment, the value of R determined in the deviated slightly from the accepted value 0.082L atm/mol K. Also in the experiment hydrogen gas was collected in a tube and measured it volume, pressure and temperature of the gas, which helps to calculate the value for R. The quantity of the gas helps to know the mass of the magnesium metal with HCl. This deviation was due to some loss of gas through the screw cap of the side flask during reaction. This error could had been avoided, by the tightening of the screw cap on to the flask and compromise between tight and a strong seal which will be hard to removed later. The error in the reaction was not all the volume of the gas in the tube was produced in the reaction. Moreover, regarding the pressure more accurate values could have obtained if barometer was allowed to be used in the laboratory. Because atmospheric pressure varied a little around the room. One of the useful procedure was when HCl was poured into the side beaker without getting any of the acid inside the neck of the flask. The pressure of the vapor provided a tangible example between ideal gas and real gas and how the concept of gas equation was applied. The theory behind this experiment was to find the value that that were closed or reasonable to the gas constant. But with the equipment and conditions was able to examine the ideal gas law. REFERENCES Dr. Dionne A. Miller Assistant Professor Chemistry Natural Science Department LaGuardia Community College....